Depends on level of the companion, but it's definitely way higher than a typical troop. I haven't seen it go above ~100 or maybe 200 for high level companions, though. Considering the max is under 10 companions it's not a lot.How much golden coins is a companion wage worth? Frankly, I never checked that.
There are situations in the game where it's not worth paying that, but they're generally in the early game.